A conventional D/A converter is known in which, when a digital value is entered thereinto from the outside thereof for every predetermined period, the digital value is sequentially converted into an analog value. However, even if the maximum D/A conversion speed of the D/A converter is very high, because the actual D/A conversion speed depends on the speed when the digital value is written thereinto from thereoutside, a problem has occurred that the actual D/A conversion speed decreases.
In Patent Document 1, a technology is disclosed for the purpose of resolving such a problem. In Patent Document 1, an analog signal processor for a programmable controller is disclosed which directly performs, based on an analog signal inputted from thereoutside, a series of actions from A/D conversion to D/A conversion without the intervention of a CPU device.